This invention relates to gas flow measurement and, more particularly, to the determination of the supercompressibility factor of a flowing gas subject to volume measurement.
The rapidly increasing cost of natural gas since the 1970's has caused profound changes in attitudes towards meter accuracy, especially when gas at high pressure is involved. Thus, increasing attention has been focused upon providing an accurate measure of the volume of gas flowing through a pipeline. However, all volumetric meters measure actual volume and, since gas is a compressible item, the volume of which changes as a function of temperature and pressure, calculations must be made to convert the measured gas flow volume to a standard volume at a specified, previously agreed upon, base condition of temperature and pressure.
U.S. Pat. No. 4,390,956, discloses an apparatus for performing the correction calculations. In that disclosed apparatus, the major part of the calculations are involved with determining the supercompressibility factor of the flowing gas, based upon measured temperature and pressure and a set of constants entered into the apparatus for a particular gas composition. Thus, if the gas composition changes, a new set of constants must be entered into the apparatus.
It is therefore an object of the present invention to provide an arrangement for determining the supercompressibility factor of a flowing gas.
It is a further object of this invention to provide such an arrangement which is automatically adaptive to changing gas compositions.